New 'Internal GPS' Uses Internal Sensors to Track Bodily Changes

Doctors might finally be able to monitor the human body in a more intimate way without the invasive operations that come 

A team from the Massachusetts Institute of Technology's Computer Science and Artificial Intelligence Laboratory (CSAIL) developed an in-body tracking system that could help doctors avoid the invasive scopes.

This "in-body GPS" system is called ReMix, and it can successfully pinpoint implants within the body and track what's going on inside. These changes could be anything from making sure tumors don't move or shift, or monitoring how medication affects an area. 

The CSAIL project was led by Professor Dina Katabi in collaboration with the Massachusetts General Hospital. Katabi and the team successfully demonstrated the implants in animal testing with centimeter-level accuracy. 

Internal Tracking for External Results

Testing ReMix required the researchers to think creatively. Katabi's team implanted small markers within animal tissue. To track the movement, the team then used a wireless device and an algorithm to pinpoint exactly where the marker was.

Unlike other sensor systems, the marker inside the tissue didn't need to transmit a signal itself. It reflected the signal given off by the wireless device found outside the tissue. This also means it doesn't require power in order to operate. 

The challenge, however, came in how to direct the wireless signal and avoid competing with the reflections found on the human body. As the researchers pointed out, the signals reflected off a person's skin are 100 million times more powerful than the signals found on the metal marker. 

The MIT team created a semiconductive device (diode) that mixes the signals together and then filters out the skin-related signals. When all signals get back to the system itself, the original frequencies that came from a patient's skin are removed. 

The team hopes to use ReMix in cancer therapy and treating tumors. One applicaiton could be proton therapy -- when oncologists bombard a tumor with protons and thus put higher levels of radiation in the body. Proton therapy requires precision. If a tumor moves during the process, then it could leave healthy tissue exposed to radiation. 

Small markers like ReMix could give doctors an incredibly accurate picture of where a tumor is in the body, and give patients safer treatment options. 

"The ability to continuously sense inside the human body has largely been a distant dream," said Romit Roy Choudhury, a professor of electrical engineering and computer science at the University of Illinois, who was not involved in the research. "One of the roadblocks has been wireless communication to a device and its continuous localization. ReMix makes a leap in this direction by showing that the wireless component of implantable devices may no longer be the bottleneck."

Future Applications

The team will continue researching how ReMix impacts patients. Next, MIT wants to combine wireless data and medical data. For example, they would allow doctors to use MRI results in conjunction with the ReMix data. The researchers also need to improve the accuracy of the algorithm itself. 

"We want a model that's technically feasible, while still complex enough to accurately represent the human body," said PhD student Deepak Vasisht, lead author on the new paper. "If we want to use this technology on actual cancer patients one day, it will have to come from better modeling a person's physical structure."

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The MIT team hopes that by making these types of treatments more accessible, more medical facilities could start offering proton therapy centers for treatment. Currently, there are only 100 centers around the world offering proton therapy, according to MIT. 

"One reason that [proton therapy] is so expensive is because of the cost of installing the hardware," says Vasisht. "If these systems can encourage more applications of the technology, there will be more demand, which will mean more therapy centers, and lower prices for patients."